Just spent a fair bit of today renovating a 1956 international tractor brakes and thought it worth a mention that here is an agri vehicle with in-board disk brakes. Made me wonder why the car industry didn't catch onto this earlier? Admittedly, they are operated by concentric steel plates with ball bearings running in grooves, but the simplicity of dismantling without major surgery is to be congratulated. Also, there are two double sided circular friction plates on each side, so the stopping power is massive (when friction material renewed!).

Inboard discs put braking thrust loads into diff and transmissions, even on race cars with trans axles (Hewland boxes etc). Also outboard generally easier to cool.
A guy fitted inboard discs to a Sierra diff ( dead easy to do actually) but heat cooled diff bearings and oil so needed oil cooler and regular rebuilds.
Also on a car with reasonable power and weight, it does funny things under braking as the discs are braked but then theres the tolerance for the CV or UJ joints meaning you end with a lead and lag braking across the axle

Always liked the idea of trying on an ss1 but the rubber mounted diff would be an issue

Racing is life, everything before and after, is just waiting--Steve McQueen
6 time Class Champ, 2006 & 2014 SSSC Champion

Quite apart from practical issues such as line of sight for inspection and proximity to the outside for ease of access and maintenance, aren't there some theoretical reasons why in board brakes may not be such a good idea - such as if anything in the transmisson downstream of the brakes fails then the brakes may not stop the runaway vehicle which rather bypasses the primary objective. As I recall, weren't there truck brakes once that clamped curved brake shoes around the centre of the driveshaft to the rear wheels? Which was fine provided the diff etc held against the momentum of the vehicle. Not sure in the 40s and 50s that the materials were necessarily to be relied upon. If the aim is not so much to stop the vehicle as to stop the wheels from turning, then the closer you get to the wheel itself the better. Mind, I doubt this sort of argument applies to your typical tractor!

On "normal" road cars I think one of the big downsides with inboard discs has always been access and visibility, for routine maintenance? Tractors share with racecars, minimal bodywork and exposed internals, making access to things like inboard brakes much easier.

....Roger

RSSOC member (since 1982)
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"Condition can be bought at any time; Originality, once lost, is gone forever" - Doug Nye